Tuesday, August 05, 2014

Rosewill RSV-S4-X and mdadm RAID5

I've had the Rosewill RSV-S4-X for about a week now. I've got it integrated into my MDADM RAID5 array using 5 2TB SATA drives. So far I think its working OK. I'd say 4 out of 5 stars. More on why that is later.

So the enclosure comes with a Silicon Image 3132 PCIe eSata expansion card. This is what does the port-multiplication. I'm currently running Ubuntu 13.10. The Sil3132 is supposed to be well supported in linux. My experience has been good in general with it. Ubuntu picked it up right away with no issue.

The enclosure itself seems to take all its queues from the card. Its default is to be in JBOD mode, which is exactly what I need for mdadm. I added 2 more 2TB HDs to the enclosure, and they showed up as /dev/sd[gh] right away. So far so good.

I had a drive fail inside the machine. I added /dev/sdg1 to the array and had it re-sync. The re-sync process was holding at a steady 70MB/s. While not blazingly fast, this seemed about normal with the speeds I was getting from the on-board SATA ports.

Cons:

So far I have only run into 2 problems with the system, and I think they're related. I originally placed the 2 drives in the top most 2 slots. This turned out to be slots 3 and 4. At first I didn't think much of it. Later on, I removed the faulty HD and ran some tests on it through WinDFT. It seemed to pass those tests fine, so I shut the system down and inserted the drive into Slot 1 of the Rosewill. I wasn't 100% sure if the rosewill was hot-swap, so I didn't take the chance.

Immediately things didn't go well. The Sil3132 was no longer being recognized. I rebooted a few times, with no change. Finally I decided to just remove the faulty drive. A few reboots later the card came back up, as did the two drives. Unfortunately by then mdadm had already removed /dev/sdg1 ( the one in the enclosure) from the array. A --re-add was refused.

My hypothesis is that by adding the drive into Slot 1, the raid card reordered the drives. This was enough to confuse mdadm, and the drive ended up being removed and the array degraded. I've since did an --add on the drive, and the array re-synced over night. I rebooted the machine a few times to ensure that it works, and things seem to be going ok.

Conclusion:

Its  a nice enclosure, and for home use I think its perfectly fine. I would be hesitant to use it in a mission-critical environment, simply because of the unknowns about drive re-ordering.

I'm especially concerned about what might happen if more of my drives are on the enclosure. If the drives re-order again, and 2 of my drives get kicked out of the RAID, then I may be in trouble. Keep good backups of everything!

I'll try to keep this post updated as I find more things. \

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